What is the Musa classification of adenomyosis in women of reproductive age?

MUSA Classification of Adenomyosis

The MUSA (Morphological Uterus Sonographic Assessment) classification system represents the current consensus-based approach for standardized ultrasound diagnosis of adenomyosis, requiring at least 2 ultrasound features for diagnosis. 1

Core MUSA Diagnostic Features

The MUSA consensus establishes specific transvaginal ultrasound criteria that must be systematically evaluated:

• Junctional zone alterations - Thickening, irregularity, or disruption of the interface between endometrium and myometrium 2
• Myometrial cysts - Small anechoic areas within the myometrium 1
• Hyperechoic islands - Bright echogenic foci in the myometrium 1
• Fan-shaped shadowing - Linear acoustic shadows radiating from the endometrium 1
• Asymmetric myometrial thickening - Unequal anterior/posterior wall thickness 2
• Globular uterine enlargement - Diffuse uterine enlargement with preserved contour 3

Classification by Topography and Extent

Adenomyosis should be classified by anatomical location (topography), morphological type, size, and extent to guide clinical management. 1

Topographic Classification

• Anterior wall adenomyosis - Involvement of the anterior myometrium 1
• Posterior wall adenomyosis - Involvement of the posterior myometrium 1
• Lateral wall adenomyosis - Involvement of the lateral myometrium 1
• Fundal adenomyosis - Involvement of the uterine fundus 1

Morphological Type

• Diffuse adenomyosis - Widespread myometrial involvement, more common in older reproductive age women (>35 years) 2
• Focal adenomyosis - Localized areas of involvement, more common in younger women (18-35 years) 2
• Adenomyoma - Well-defined nodular lesion within the myometrium, significantly more frequent in advanced reproductive age (16.4% vs. 1.6%) 2

Severity Grading

• Mild adenomyosis - Limited myometrial involvement, more prevalent in early reproductive age 2
• Moderate adenomyosis - Intermediate myometrial involvement 1
• Severe adenomyosis - Extensive myometrial involvement, more common in advanced reproductive age (24.7% vs. 9.8%) 2

Diagnostic Performance and Validation

• Transvaginal ultrasound using MUSA criteria demonstrates 82.5% sensitivity and 84.6% specificity for adenomyosis diagnosis 4
• The MUSA-based classification shows substantial to almost perfect agreement with histopathology - Cohen's kappa of 0.703 for topography, 0.896 for type, 0.892 for extent, and 0.898 for size 1
• MRI should be reserved for cases where ultrasound findings are indeterminate or the uterus is incompletely visualized, as it can display the endometrium even when obscured on ultrasound 4

Clinical Correlation with Age and Symptoms

Young women (18-35 years) present with distinct adenomyosis patterns compared to older women, requiring age-specific diagnostic awareness:

• Severe dysmenorrhea predominates in early reproductive age (78.7% vs. 54.8%), with focal and mild adenomyosis patterns 2
• Menorrhagia is more characteristic of advanced reproductive age (64.4% vs. 37.7%), associated with diffuse and severe patterns 2
• Altered junctional zone is significantly more common in older women (67.1% vs. 39.3%) 2

Integration with Other Classification Systems

• Adenomyosis is recognized as a specific entity in the PALM-COEIN FIGO classification of abnormal uterine bleeding causes 3
• Deep endometriosis classification includes adenomyosis as lesions extending >5mm under the peritoneal surface, though adenomyosis remains a distinct entity 5
• Adenomyosis frequently coexists with endometriosis and fibroids, requiring comprehensive evaluation for concurrent pathology 3, 6

Critical Implementation Points

The MUSA classification enables standardized interpersonal communication between clinicians, prognostication about disease severity, and assessment of surgical candidacy. 1

• Diagnosis requires systematic documentation of all MUSA features present, not just a binary adenomyosis present/absent determination 1
• Early diagnosis in young women may interrupt disease progression mechanisms, as adenomyosis appears to have early onset during adolescence with tendency to progress over time 7, 2
• Screen for concomitant deep endometriosis, especially in the posterior compartment, when adenomyosis is diagnosed 7